It is my belief that M1 5W-30EP contains at least some AN base stock. By percentage, I can't say, but the pour point reflects this. AN's make great extended drain and high temp oils. AN’s unique chemical properties enhance the effectiveness of additive packages, allowing even modest formulations to perform exceptionally well. AN's superb thermal stability is right for turbocharged engines.
All of us here know it is about impossible to get a handle on the ingredients. So we do our best estimate what's inside, with widely varying opinions. I believe EP has AN in it. Others swear that it is just a Group III oil. Yet Mobil makes the bold claim that the 5W-30EP has 5000x better high temperature performance. (a little joke but they do claim 20x) Mobil references the sequence IIIH test about deposits and oxidation along with how well an oil maintains its viscosity and keeps engine components clean under high-temperature and high-load conditions. That screams AN.
But when we boil it down, the idea that one example of a high quality 5W-30 is significantly better than another is likely to be wrong under normal OCI's. What's more critical is viscosity choice.
I use the EP because it works amazingly well for me. If the 5W-30 is a little shy in viscosity, a move to 10W-30EP is a very minor step up.
